88 SPCL Overheating only at higher RPMs.

[Booster72169]

Ok guys I need some help. My father and I have been working on an 88 model 88SPCL. The heat buzzer goes off if you try to run it above 5000 rpms for very long but doesn't if you stay below that. We have installed a new impeller, pulled the thermostats and cut the centers out ( done comonly around salt water ), and pulled the heads and head cover plates to make sure there was nothing restricting water flow in the water passages. The last thing my dad tried was to pull the hoses going to the thermostat housings and just let them dump in the pan. This was successful.

I guess my question is what could be restricting the water flow between the thermostats and dumping the water through thid mid section in the exhaust? Can anybody think of anything else we can try?

[ELGIN]

Salt water build up in the cooling passages?

[Booster72169]

There was no build up in the block or heads. Everything appears to be wide open on the up flow of the water. It just seems like there is a restriction on the down flow making this thing hold the water too long and making it overheat at higher rpms. Like I said if you disconnect the hoses coming from the heads going to the thermostats and just let it dump the water in the pan it does not overrheat.

Anything else anybody can think of?

Also as far as we know this is not a salt water motor. Just cut the centers out of the thermstats trying to get a little more water flow.

[ELGIN]

The adapter plate is a good place for salt, sand, or mud build up, if you feel its a down flow issue pull the powerhead and check the passages.

[Booster72169]

Thanks.....That is kinda what we were thinking but running out of time. My cousin is coming to pick this boat up this weekend and we were just trying to get everything worked out before he hauls it back to Phoenix, AZ. He may just have to figure this out on his own when he gets it home.

Thanks for the suggestions and I love all the help you guys give us.